A. Field of the Invention
Embodiments of the claimed subject matter relate to methods, systems and apparatuses for purifying air, and more particularly, to systems, methods and apparatuses for removing particles and contaminants from an air flow by attracting the particles and contaminants to charged spray droplets of a fluid introduced to the air flow.
B. Description of Related Art
The technique of electrospray ionization is well described and known to those skilled in the art. Prior art air purification apparatuses and methods include U.S. Pat. No. RE 30,479 to Cohen, et al. which illustrates a method for the removal of particulate matter as well as noxious gases and vapors from a gas stream. This is accomplished by means of charged droplets having a size between 60 and 250 microns and preferably between 80 and 120 microns. The droplets are generated by first ejecting a stable jet of liquid such as water and the liquid jet is broken up into charged droplets by applying an electric potential between the jet and the collecting walls of the scrubber.
U.S. Pat. No. 4,095,962 to Richards describes a method for producing small highly charged droplets without concurrent production of corona by conducting a liquid to a nozzle having a tip from which droplets of the liquid can exit, and forming a substantially uniform electric field over the surface of the liquid on the tip, the field being large enough to pull off droplets from the tip but not so large as to create corona discharge. Selected gas, solid particulates and liquid mists from gaseous effluents such as are produced by smelters, coal or oil-burning steam generators, chemical refineries and the like are removed by means of a unique electrostatic collector using the highly charged droplets. These droplets are caused to drift, by means of an electric field, through the gaseous effluent to a collecting electrode absorbing selected gases and aerosol particles and carrying them to a collecting electrode.
U.S. Pat. No. 6,156,098 to Richards describes a gas scrubbing apparatus and method, employing highly charged liquid droplets for removal of both particulates and pollutant gases from the gas to be cleaned, that allows scrubbing of uncharged particulates by means of monopole-dipole attractive forces between the charged liquid droplets and the electric dipoles induced in the uncharged particulates by the charged droplets. It also describes employing electrode geometry at the site of droplet production and charging, having spreading liquid sheet electrodes emitting the droplets from the edges of the liquid sheets, interspersed with electrically conductive induction electrodes, with electrostatic potential of no more than about 20 kv existing between the induction electrode array and the array of liquid sheets, and with spacing such that adequately high electric field strength can be maintained at the edges of the liquid sheets to allow adequate charging of the droplets emitted from the liquid sheets, without the occurrence of corona discharges which could deplete droplet charges or interfere with production of the electric field strength required for adequate droplet charging; allowing the particulate and pollutant gas scrubbing procedures to be carried out simultaneously in a single chamber; requiring no substantial power other than that for the blower or other means which moves the gas to be cleaned through the cleaning chamber; and allowing these results to be achieved with low liquid-to-gas flow ratios.
Next, U.S. Pat. No. 6,471,753 (Ahn, et al.) discloses a device for collecting dust using highly charged hyperfine liquid droplets formed through an electro-hydrodynamic atomization process. In the dust collecting device of this invention, a high voltage is applied to capillaries, set within a dust guide duct and having nozzles at their tips. An electric field is thus formed between the capillaries and the duct, and allows the nozzles to spray highly charged hyperfine liquid droplets. Such liquid droplets absorb dust laden in air, flowing in the duct by suction force of a fan. An electrostatic dust collector is detachably coupled to the duct while being insulated from the duct, and forms an electric field having polarity opposite to that of the highly charged liquid droplets, thus electrostatically collecting and removing the dust absorbed by the highly charged liquid droplets. The dust collecting device of this invention easily and effectively removes fine dust having a size smaller than 0.1 cm. This device is also preferably operable at low cost while achieving a desired dust collection effect, and is collaterally advantageous in that it humidifies discharged air, when water is used as the liquid for atomization of the hyperfine liquid droplets.
Willey, et al. (U.S. Pat. No. 6,656,253 and U.S. Pub. No. 2003/0196552) disclose an apparatus for removing particles from air which includes an inlet for receiving a flow of air, a first chamber in flow communication with the inlet, wherein a charged spray of semiconducting fluid droplets having a first polarity is introduced to the air flow so that the particles are electrostatically attracted to and retained by the spray droplets, and an outlet in flow communication with the first chamber, wherein the air flow exits the apparatus substantially free of the particles. The first chamber of the apparatus further includes a collecting surface for attracting the spray droplets, a power supply, and a spray nozzle connected to the power supply for receiving fluid and producing the spray droplets therefrom. The apparatus may also include a second chamber in flow communication with the inlet at a first end and the first chamber at a second end, wherein particles entrained in the air flow are charged with a second polarity opposite the first polarity prior to the air flow entering the first chamber.
U.S. Published Application No. 2004/0023411 to Fenn describes a method of collecting or “gettering” polar trace species from ambient air devoid of the need for forced convention or pumping of the air sample. This invention utilizes a specialized electrospray source, fed by a wick, which attracts and transfers surface charge from spray droplets to ambient polar molecules and particulates which migrate into the path of the electrospray jet source and the target. Collected species may be detected directly on collection surface using suitable detection methodologies or can be stored for subsequent analysis.
The Richards '803 patent (U.S. Pat. No. 6,986,803) describes a process and apparatus for gas cleaning, as in HVAC systems or semiconductor manufacturing clean rooms, for removing 99.999% of particulate and gaseous contaminants, which may be effectively used to remove and neutralize Bio-chem agents introduced by terrorists, having a first stage in which large quantities of positively charged liquid droplets are introduced into the gas to be cleaned so as to remove virtually all negatively charged particulates and at least 90% of neutral particulates and soluble gases; a second stage in which most positively charged droplets from the first stage are removed and remaining particulates are given a positive charge; a third stage in which large quantities of negatively charged liquid droplets are introduced to remove positively charged particulates and more soluble gas contaminants; and a fourth stage in which the negatively charged droplets are removed from the cleaned gas stream.
In use, known air filters used for personal protection and air purification do not allow for sufficient air circulation and heat stress is a significant issue that affects the health, safety, and operational performance of the Soldier, Marine, Sailor, Airman, and Emergency Responder. One issue is the prior art's inability to reject metabolic body heat to the environment due to the insulation characteristics of their personal protective clothing. As a result, body heat is stored, core temperature rises and operational performance can become severely impaired. In collective protection applications, mechanical filters such as High-Efficiency Particulate Air (HEPA) or Ultra Low Penetrating Air (ULPA) produce a large pressure drop and significant stress on ducting. They are not universally effective at removing various classifications of contaminants (e.g. bacterial spores versus chemicals). Finally, they are bulky and costly, requiring large blowers and the filters are consumables and, once used, must be disposed of as hazardous waste. Embodiments of the present invention attempt to address the aforementioned issues found in the prior art.